With Alexander in India we have nothing to do in these pages. It is as the first explorer in the regions beyond India, the Afghan and Baluchistan hinterlands, that he at present concerns us; and it may fairly be stated that no later expedition combining scientific research with military conquest ever added more to the sum of the world's knowledge of those regions than that led by Alexander. For centuries after it no light arises on the geographical horizon of the Indian border. Indeed, not until political exigencies caused by Russia's steady advance towards India compelled a revision of political boundaries in Persia, Baluchistan, Afghanistan, and India, was any very accurate idea obtained of the geographical conditions of Northern and Western Afghanistan, or of Baluchistan, or of Southern Persia. The mapping of these countries has been recent, and the progress of it, as year by year the network of Indian triangulation and topography spread westward and northward, has reopened many sources of light which, if not altogether new, have lain hidden ever since the Macedonian conqueror passed over them. Long before the Greek army mustered on the banks of the Hellespont we have seen that the highways to the East were well trodden and well known. It was not likely that Alexander's intelligence department was lacking in information. For many centuries subsequent to that expedition the rise of the Parthian power absolutely cut off these old-world trade communications and set the restless tides of human emigration into new channels. But in Alexander's time there was nothing in Persia to interrupt the interchange of courtesies between East and West.
The great Aryan tide had already flowed from the Central Asian highlands into India, but Jutes and Skyths had yet to make that great drift westward which peopled half of Europe with nomadic tribes speaking kindred tongues--a drift which never rested in its westward advance till, as Anglians and Saxons, it had enveloped England and faced its final destiny in an American continent. Assyria had passed by with arts and commerce rather than with arms, and Persia had followed in Assyrian tracks. Both had established colonies half-way to India in the Afghan highlands, Persia with the aid of captive Greeks, and Assyria with people taken from the Syrian land. The list of Assyrian and Persian satrapies included all those lands which we now call the hinterland of India, and which in Alexander's time must have been absolutely Persianized. But beyond the historical evidence which can be collected to prove the early, the constant, traffic which ensued between Mesopotamia, or Asia Minor, and India, after the consolidation of those two great empires, there is the tradition which certain Greek writers (notably Arrian) treat rather scornfully, of the conquest of Upper India by the mythical hero Bacchus. It is never wise to treat any tradition scornfully, and Arrian is himself obliged to admit the difficulty of explaining certain records connected with Alexander's history, without assuming that the tradition was not groundless.